1. Field of the Invention
The present invention relates, for example, to a mechanism for wireless networks such as IEEE 802.11 to enable roaming queries prior to association/authentication while maintaining the advantages of power saving mechanisms.
2. Description of the Related Art
When wireless local area network (WLAN) access points are shared by multiple service providers (e.g. in the case of airport hotspots in which the airport owns the access point, but service is provided by other operators, such as T-Mobile), a technique called “virtual AP” can be used to allow sharing of the access point. From the mobile station's point of view it is as if there were several different access points. Multiple service set identifiers SSIDs can be used by the same access point to support the different service providers.
In traditional roaming cases, the mobile station has a roaming client (e.g. T-Mobile™ connection manager, Boingo™ connection manager, or the like) that has a roaming directory. The roaming directory can be a list of SSIDs for access points to which the station can connect. For a mobile station to select the access point and connect, a valid SSID must be used. Thus, the access point should broadcast that SSID and the mobile station should know it. In other words, currently the burden of determining whether the mobile station can or cannot access a given access point based on a roaming agreement is left completely to the mobile station, and is traditionally solved by downloading a long list of SSIDs to the mobile station.
With current virtual AP solutions, the access point cannot simultaneously broadcast all the SSIDs supported. Therefore, if the mobile station does not detect a supported SSID in the beacons, the mobile station must perform active scanning: it must send a Probe Request to the access point providing a given SSID. If the access point supports it, it will return a positive answer. When roaming, the list of the mobile station preferred SSIDs can be rather long, which can result in extensive signaling to obtain a valid SSID. For example, a mobile station may have 200 SSIDs, which is not an unusual number, and only the 189th may be supported. Thus, in such a circumstance, the mobile station must perform 189 queries. Optimizations have been proposed according to which a list of SSIDs can be provided in beacons and Probe Response messages. However, the list is still limited, and therefore the problem still exists.
Some ideas have been presented to extend the Probe Request and Probe Response frames in such a way that the mobile station can query the network for roaming information or alternatively to define two new management frames to carry the request and the reply. Two options are possible: the mobile station queries for what realms are supported (not realistic, e.g. the list may be very long and therefore the solution does not scale), or the mobile station queries the network using its own Roaming ID and the network replies either yes or no. The second option is more realistic, but has a drawback: the access point may have to retrieve the information from the back end before being able to provide the information to the station, since it is not realistic to expect the access point to be preconfigured with all roaming info. Therefore, the access point may not be able to reply instantaneously to the mobile station request. However, it may be necessary that the Probe Response shall be sent to the mobile station no later than a very short period of time (e.g. 5 ms, as currently defined in the WiFi Alliance) from the receipt of the Probe Request. This requirement may be needed for power saving reasons.
There is the need to allow a mobile station to discover whether it has roaming in a certain access point (AP) without the need for the mobile station to try to authenticate/associate and without requiring continuous probing for different service set identifiers (SSIDs).
Another scenario in which improvement may be required may be in the support of wireless information services, for example, 802.21 Information Service (IS) in 802.11. The idea is to allow the mobile station to access IS information before authentication/association so that the mobile station can decide whether or not it wants to connect. Support of wireless information services such as 802.21 Information Service may require that Probe Request and Probe Response information carry the queries and replies, such as 802.21 IS queries and replies. Solutions are needed to enable this function, since the queries are typically not processed by the access point but by an information server, such as an 802.21 server in the network, and therefore the reply may not be available within a very short period of time from the receipt of the Probe Request.
It may also be important to be able to identify services that are available from an access point before attachment, specifically for information defined in wireless network information services standards, such as IEEE 802.21 Information Service.